Multi-Band PWM Signal Generation Without Spurious RF Tones
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Solution Overview
Problem
Conventional RF transmitters face challenges in generating multi-band signals for concurrent non-contiguous operation due to limited bandwidth and the complexity of multi-level pulse width modulation (PWM) encoders and power amplifiers, leading to increased size and cost, as well as issues with spurious tones in RF transformation.
Innovation Solution
The method involves transforming multiple base-band envelope signals into a sequence of symbols, which are then encoded and amplified using multiple PWM encoders and power amplifiers, allowing for the generation of a multi-band signal by combining the amplified signals, thereby reducing complexity and avoiding spurious tones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple transmitters are used to generate multi-band signals, then bandwidth coverage is improved, but device size and cost increase
Solution Approach 1:
The patent combines multiple base-band envelope signals into a single multi-band signal using digital signal processing. Multiple PWM encoders and power amplifiers are merged into one transmitter unit, allowing concurrent transmission on multiple disjoint frequency bands without requiring separate transmitter hardware for each band.
Solution Approach 2:
The transmitter is designed with multi-functional capability to handle multiple disjoint frequency bands simultaneously. The digital signal processing architecture and multiple PWM encoders enable the single transmitter to perform functions that would traditionally require multiple dedicated transmitters, achieving universal multi-band operation.
2Adaptability or versatility
If multiple transmitters are used to generate multi-band signals, then bandwidth coverage is improved, but cost increases
Solution Approach 1:
The patent combines multiple base-band envelope signals into a single multi-band signal using digital signal processing. Multiple PWM encoders and power amplifiers are merged into one transmitter unit, allowing concurrent transmission on multiple disjoint frequency bands without requiring separate transmitter hardware for each band.
Solution Approach 2:
The transmitter is designed with multi-functional capability to handle multiple disjoint frequency bands simultaneously. The digital signal processing architecture and multiple PWM encoders enable the single transmitter to perform functions that would traditionally require multiple dedicated transmitters, achieving universal multi-band operation.
3Adaptability or versatility
If base-band envelope signals are encoded with RF upsampling, then multi-band transmission is enabled, but spurious tones are generated
Solution Approach 1:
The patent inverts the conventional processing order by performing RF transformation before encoding instead of encoding after RF upsampling. This reversal of the processing sequence eliminates the generation of spurious tones while maintaining multi-band transmission capability. The PWM encoding is applied to the transformed signal rather than to upsampled base-band signals.
Data Source
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AI summary
A method for generating a multi-band signal transforms multiple base-band envelope signals into a sequence of symbols representing a signal including a plurality of disjoint frequency bands. Each frequency band corresponds to a single base-band envelope signal. Each symbol corresponds to amplitude of the signal and is a number selected from a finite set of numbers. The method encodes the sequence of symbols as a plurality of pulse width modulation (PWM) signals. Each PWM signal includes a plurality of codes for encoding each symbol, such that a sum of values of the codes of the set of PWM signals encoding a symbol is proportional to a value of the symbol. The method amplifies the PWM signals to produce a plurality of amplified signals and combines the amplified signals to produce the multi-band signal.